Definition of "Impulsive" :

adjective: characterized by undue haste and lack of thought or deliberation

"Liable to such impulsive acts as hugging strangers."

adjective: determined by chance or impulse or whim rather than by necessity or reason

adjective: having the power of driving or impelling

"An impulsive force."

adjective: without forethought

"Letting him borrow her car was an impulsive act that she immediately regretted."

adjective: proceeding from natural feeling or impulse without external stimulus

"An impulsive gesture of affection."